# Regular Expression Denial of Service in Leo Editor

Advisory record · `GHSA-x38q-xg2h-rxgx`

- **Identifiers:** `GHSA-x38q-xg2h-rxgx` · `CVE-2020-23478` · `PYSEC-2021-338`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-697](https://cwe.mitre.org/data/definitions/697.html) · [CWE-1333](https://cwe.mitre.org/data/definitions/1333.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md) · [CWE-697](https://agentprime.io/advisories/tag/cwe-697.md)
- **Published:** 23 Sept 2021
- **Updated:** 27 Sept 2024
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 23 Sept 2021, 23:14 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `leo` (PyPI): affected `<6.3`; fixed in `6.3`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`, from GitHub Advisory Database

- **CISA KEV:** Not listed.
- **EPSS:** 0.012, the 69th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 23 Sept 2021. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-x38q-xg2h-rxgx](https://github.com/advisories/GHSA-x38q-xg2h-rxgx)
- [OSV: GHSA-x38q-xg2h-rxgx](https://osv.dev/vulnerability/GHSA-x38q-xg2h-rxgx)
- <https://nvd.nist.gov/vuln/detail/CVE-2020-23478>
- <https://github.com/leo-editor/leo-editor/issues/1597>
- <https://github.com/leo-editor/leo-editor/commit/029833689060ee73f1bc1708cf4b182f0c66ec8e>
- <https://github.com/advisories/GHSA-x38q-xg2h-rxgx>
- <https://github.com/leo-editor/leo-editor>
- <https://github.com/pypa/advisory-database/tree/main/vulns/leo/PYSEC-2021-338.yaml>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-x38q-xg2h-rxgx>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-x38q-xg2h-rxgx/>. Everything for agents: <https://agentprime.io/llms.txt>.